My daughter is very interested in chemistry, which reminds me of my own interest in this subject when I was a child. To follow her interest, we decided that we learn a bit about basics of chemistry this summer through online videos and simple science experiments. The experiments will be equally enjoyable for younger kids, but I think only kids over age 7 or so will be able to appreciate what is happening “behind the scenes” here.

Do Molecules Attract Each Other?

My daughter is very interested in science, and she is also relatively well read. Unfortunately, a lot of books she reads, especially books with science experiments, don’t really “connect the dots”. As a result, a lot of scientific knowledge makes up quite an amazing stew of right facts and wrong conclusions in her head. An example of this came in our discussion:
Me: What do you think chemistry studies?
Smarty (confidently): Chemicals and chemical reactions!
Me: OK. What are chemicals?
Smarty: Umm… Everything.
Me: What is “everything” made of?
Smarty: Atoms and molecules?
Me: What is smaller – an atom or a molecule?
Smarty: An atom, I think. Molecules are made of atoms. And then there are protons, and electrons, and…. something else too.
Me: This is good. Do you think molecules attract each other or repel each other?
Smarty: Repel. I remember reading that they have a positive and negative charge.
Me: Then how do you think matter stays together?
Smarty: Hmm… I don’t know. Maybe molecules repel only in gases?

Watch Molecules Attract

You need only the simplest materials to demonstrate that molecules do in fact attract each other. In fact, you need nothing more than water and a dropper, but we added extra fun by coloring water with food coloring and dropping water on a waxed sheet of paper. You can find a more detailed lesson plan (and an activity sheet) here, but I went through an abbreviated version with Smarty.

Observe how the drop of water keeps its shape coming out of a medicine dropper and doesn’t just trickle down in a stream.

Observe how water drops come together on a waxed sheet instead of spreading in a thin flat puddle on a sheet.

Observe how drops easily join together (and mix into one color).

Observer how you need to apply significant force (blowing or pushing with a dropper) to separate a puddle into more than one puddles.

Smarty really enjoyed playing with colored water. She acknowledged after demonstration that molecules indeed attract to each other. By the way, her understanding of molecular charge was surprising to me, but her interpretation was way off.

Play "Water Drops Unite"

Smarty was thrilled to be able to play a game during this science lesson. I printed out an activity sheet for the game from Middle School Chemistry site. We played the game both cooperatively trying to join all the drops in the center and competitively when each of us controlled drops of one color and we tried to keep them away from each other and control the center at the same time. All in all, an experiment that took 5 minutes to set up resulted in an hour of science play. Smarty wanted to do more, but we needed to leave for her tennis class.

Watch an Amazing Slow Motion Video

What happens to a water balloon when it pops? It actually keeps its shape for a moment due to molecular attraction forces. See it for yourself!

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